Old TV Spectrum Is New Internet Frontier

U.K. telecommunications regulator Ofcom published Thursday proposals for how so-called “white space” — frequency gaps opened up when old analog TV was switched off — will operate. It could herald the next phase of the Internet, a place where machines talk to machines.

The “Internet of Things” concept describes the prospect that in a decade or so, the number of Internet-connected devices could be as high as 50 billion, mostly comprising remote sensors monitoring a simple thing, such as stresses in a bridge, or how many cans of drink are left in a vending machine.

But how will all these devices relay back their information? Radio-frequency spectrum is scarce, valuable, and under a lot of pressure. Ways have to be found to make the maximum use of what there is.

As such, white space offers a way of fitting in the maximum number of devices. Think of your spectrum as a large pot into which you have to get as much as you can.

At the heart of Ofcom’s plan is to allow a mix of two main groups in this spectrum: licensed and unlicensed devices. Most of the licensed users will be digital-TV broadcasters (known as multiplexes). In addition, Ofcom licenses what it calls program-making and special events, or PMSE, equipment, such as radio microphones and audio devices. Licensed devices operate on known, fixed, frequencies.

Think of these as large stones. Put them into your pot and it may well appear full; they are going to take up most of the space. But look closely and you see lots of gaps in between them. It is into those gaps — the white space — that the unlicensed devices must fit.

But how to stop them from interfering with each other, or with the licensed devices? You don’t want your drink-machine sensor getting in the way of Celebrity Big Brother, after all.

This is where it starts to get clever. The unlicensed devices will be in a dynamic free-for-all to find clear frequencies so as to avoid each other, and avoid the existing big users. Think of them as fine grains of sand; pouring them in fills the gaps between the big rocks, flowing into every available space.

To do this, these low-power devices have to do what is known as dynamic frequency allocation; rather than sitting on one fixed frequency (like a radio station), they jump up and down finding new ones on which to broadcast as devices come and go.

The heart of such a system is a constantly updated database that keeps track, in real-time, of what devices are where, what frequencies are available, which ones are taken up by the big players, and then dividing up what is left. This database will be in constant communication with all of the base stations in its area.

“When a device first joins a network, it has to listen out for a base station to talk to,” said William Webb, chief technology officer of Cambridge-based Neul, one of the companies that has already sprung up to exploit white space. ”When it finds one, the base station will negotiate with the database as to what bands are available and then pass that on to the device.”

Base stations check in for updates every 15 minutes.

While multiplexes are unlikely to change, PMSE devices may well come and go. Imagine a rock concert taking place over a weekend. Since the concert is a licensed user, it takes precedent and pushes anyone else off its frequencies.

Ofcom’s proposals are out for consultation until the New Year. Still, Mr. Webb said, it isn’t expected that many changes will be necessary. If the regulator’s plans are accepted, then the first white-space devices could be operational as soon as the middle of next year.

It isn’t just the Internet of Things that will use white-space frequencies. Ofcom’s proposals talk of things like rural broadband (as the freed-up frequencies were occupied by TV stations, they have great reach and can easily pass through buildings) or in-home broadband.

But it is the Internet of Things that is the most exciting application, potentially opening up a whole new area of growth and allowing much talked-about concepts like smart cities and intelligent grids to come to fruition.

Comments (1 of 1)

What is the real world value of a vending machine that e-mails home that it sold 3/4s of its inventory? In the end, some guy has to refill it anyway, and any machine that is selling so poorly that it doesn't e-mail home for more inventory probably isn't worth keeping in inventory anway. Much of the perceived George Jetson universe is like this. Yes, you can create the tech to monitor remotely a thousand tiny interactions, but why? In reality, I don't need my refrigerator to e-mail me that the milk is gone, because in the end, I am the one who threw it out. As for monitoring a bridge ... well, I guess that we could do that instead of maintaining them. I mean we have been failing to maintain them without monitoring, which has gone poorly for some people in Minnesota, and almost as poorly for many others, but knowing the bridge is falling down will not actually maintain the bridge. I just wonder what the uses will really end up being. Probably faster ways of the government monitoring our lives.

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